1. Field of the Invention
The invention relates to a flange unit for the active suppression of vibrations, the flange unit being arranged between a vibration generator and a rigid structure.
2. Discussion of the Related Art
A vibration damping device is known from JP 59-65640 A1 which in automotive technology is installed between the motor vehicle engine and the body of the vehicle. This vibration damping device comprises a combination of an electrostrictive element as well as a rubber-like elastic section. The electrostrictive element is exposed to a changing voltage, the cycle of which corresponds to that of the vibration curve of the transmitted vibrations. This is to result in a mutual elimination of the vibrations caused by the deflection of the electrostrictive element and of the unwanted vibrations of the motor vehicle engine.
Asynchronous high-frequency vibrations or low-frequency vibrations caused by shaking are additionally absorbed by the rubber-like elastic sections.
DE 39 39 822 C2 also describes an active vibration damping system for a motor vehicle. In this case, a piezo-ceramic actuator comprising several individual elements is used which are layered one above the other in such a way that they form a pillar acting as an elongator surrounded by a bourdon tube. Disturbance vibrations detected by a sensor are directed to a control unit and the signals passed to the piezo-ceramic actuator as control variables.
These vibration damping systems usable in motor vehicles are not generally usable and are also unsuitable for taking transverse forces into consideration.
It is known from DE 43 10 825 C1 and DE 195 24 080 C1, in the case of a rod with a tubular wall made of carbon fibre composite, to arrange an actively controllable pressure-generating element within the rod or on the outside and in the interior of the rod. Such an actively controllable pressure-generating element then abuts on the face side against pressure discs which abut against the face sides of the two rod elements. In the case of DE 43 10 825 C1, above the region of the actively controllable element on the outside of the tubular wall of the rod, a bushing is arranged which engages over the adjoining ends of two rod elements, is adhered to these and acts as a spring, through which restoring forces are exerted.
In DE 195 24 080 C1, a ring-shaped pressure-generating element, which is actively controllable, is arranged on the outside in the region of the separating gap between two rod elements. This element abuts on the face side against shoulders formed by elements lying on the adjoining ends of the rod elements and firmly connected to the surface of the rod elements. The two rod elements are axially guided by the ring-shaped pressure-generating element. The two rod elements are pressed away from one another for the cylindrical ring-shaped element. The likewise axially active, second pressure-generating element provided in the interior of the rod between the two rod elements acts against this force. This second element has fibre loops engaging over it on both sides which are directed over dome-shaped projections. The loops are preferably displaced at 90.degree. relative to one another. A change in length of the inner axially acting, pressure-generating element is transferred to the two rod elements via the loops. Such a change in length pulls the two rod elements together.
A piezo-element is preferably used in the two publications (DE 43 10 825 C1, DE 195 24 080 C1) for the pressure-generating elements.
The rods described in the two publications are principally installed in latticework structures and, fitted with a corresponding control means, can suppress vibrations of the latticework there. The rods may be passively heavily loaded and are actively operated in a desired load range. However, it is not always possible to build vibration generators, e.g. driving motors, into latticework structures so as to enable vibrations to be suppressed with active rods such as those described in the two publications.
Rather, it is frequently the case that such vibration generators or driving elements are fastened to structures of a different type, e.g. box structures. It has been shown that in that case any active influence may then only be made on the fastening of the structures on the vibration generators or the seat of the driving elements.